Nokea
What characterizes bases or alkaline solutions?
- A. Hydrogen acceptors
- B. Solutions of low pH
- C. Hydrogen donors
- D. Amphoteric
Correct Answer: A
Rationale: Bases or alkaline solutions are characterized by their ability to accept protons (hydrogen ions), making them hydrogen acceptors. When a base reacts with an acid, it accepts protons from the acid, forming water and a salt. This property distinguishes bases from acids, which donate protons. Therefore, the correct choice is A, as bases do not donate protons but instead accept them. This property allows bases to neutralize acids and regulate pH levels in solutions, making them crucial in maintaining the balance of acidity and alkalinity in various chemical systems.
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What is pH?
- A. The measure of concentration of H₃O⺠ions
- B. The measure of concentration of hydrogen ions
- C. The measure of concentration of Hâ‚‚O molecules
- D. None of the above
Correct Answer: A
Rationale: The correct answer is 'A: The measure of concentration of H₃O⺠ions.' pH is a measure of the concentration of hydronium ions (H₃Oâº) in a solution, indicating the acidity or alkalinity on a scale from 0 to 14. Values below 7 are acidic, 7 is neutral, and above 7 is alkaline/basic. Choice B is incorrect as pH specifically measures hydronium ions, not hydrogen atoms. Choice C refers to water (Hâ‚‚O), which is not directly related to pH measurement.
Which of the following statements about dissociation is false?
- A. It is reversible.
- B. Ions are not present.
- C. It involves molecules separating.
- D. None of the above.
Correct Answer: B
Rationale: The correct answer is B - 'Ions are not present.' Dissociation involves the separation of molecules into ions. It is a reversible process where molecules break apart into ions. Choice A is true as dissociation is reversible, and Choice C is accurate as it correctly describes the process of dissociation. Therefore, the false statement is that ions are not present during dissociation.
Which type of bond involves atoms gaining or losing electrons?
- A. Ionic
- B. Covalent
- C. Both
- D. Neither
Correct Answer: A
Rationale: Ionic bonds involve the transfer of electrons between atoms, leading to one atom gaining electrons (becoming negatively charged) while the other loses electrons (becoming positively charged). This results in the formation of ions that are held together by electrostatic forces, creating an ionic bond. In a covalent bond, atoms share electrons rather than gaining or losing them, making option A, 'Ionic,' the correct answer to this question. Therefore, the correct answer is 'Ionic,' as it specifically involves gaining or losing electrons to form a bond.
What occurs to an atom that has a positive charge?
- A. Gained an electron.
- B. Lost an electron.
- C. Gained a proton.
- D. Lost a proton.
Correct Answer: B
Rationale: When an atom has a positive charge, it indicates that it has lost an electron. Electrons carry a negative charge, so the absence of an electron leads to a net positive charge for the atom. Gaining a proton or losing a proton would modify the atom's identity by changing its atomic number, but it would not directly result in a positive charge. Therefore, the correct response is that the atom lost an electron to acquire a positive charge.
Which subatomic particle can always be used to identify an atom?
- A. Protons
- B. Neutrons
- C. Electrons
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Protons. Protons are positively charged subatomic particles found in the nucleus of an atom. The number of protons in an atom's nucleus determines the element's identity. While neutrons and electrons are also essential components of an atom, it is the number of protons that uniquely identifies the element. Therefore, protons can always be used to identify an atom.